IS on 600mm Lens?

[mson]

I'll never be able to afford this lens, but isn't IS on a 600mm lens pretty much worhtless? It would be next to impossible to hand hold something like this.

http://www.bhphotovideo.com/bnh/controller/home?O=NavBar&A=getItemDetail&Q=&sku=186153&is=USA &si=acc#goto_itemInfo

[CyberDyneSystems]

Most of Canpon's IS lenses recomend IS when mounted on a tripod or monopod. A lens at 600mm will magnify any slight movement that a tripod mounted lens will generate either from your hand on the camera,. or from the shutter release/mirror slap itself. In fact,. the IS on these long telephots has been specifically tuned to counteract the effects f mirror slap.